Water treatment is needed in a variety of applications. Untreated water provides a hospitable environment for the growth of bacteria, algae, and other undesirable and potentially unhealthful organisms. It has become common practice to treat water on a periodic or continuous basis by introducing treatment chemicals to control such organisms.
Chemical feeders have been developed for bringing water into contact with solid, dry treatment chemicals so that the chemical material is dissolved in the water in a controlled manner. In a typical application of a chemical feeder, the feeder dissolves solid pellets of calcium hypochlorite (cal hypo) to introduce chlorine into the water stream; the quantity of chlorine in the water is generally expressed as a concentration of free available chlorine (FAC). An effective feeder design must provide dissolution at a desired rate, so as to maintain the desired FAC concentration, while avoiding undesirable deposits or residues; this is especially important in the case of cal hypo which produces calcium carbonate deposits. In particular, it is desirable to implement a chemical feeder that can continuously deliver a high concentration of FAC for an extended period of unattended operation.